1. Field of the Invention
The present invention relates to a lithium ion secondary battery.
2. Related Background Art
Lithium ion secondary batteries having a pair of electrodes and a separator provided in between the electrodes have been known in the past. Each electrode has a collector and an active material layer provided over the collector.
With these lithium ion secondary batteries, the heat generated when a puncture test is conducted needs to be kept sufficiently low.
Attempts at suppressing heat generation have included providing a back coating layer to the outside of the battery, as in Japanese Laid-Open Patent Application 2003-257496, or increasing the strength of the separator, as in Japanese Laid-Open Patent Applications 2000-173659 and H11-181134, for example.